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  <title>Selects the default database for database queries</title>
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  <div id="layout-content"><div id="function.maxdb-select-db" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">maxdb_select_db</h1>
  <h1 class="refname">maxdb::select_db</h1>
  <p class="verinfo">(PECL maxdb &gt;= 1.0)</p><p class="refpurpose"><span class="refname">maxdb_select_db</span> -- <span class="refname">maxdb::select_db</span> &mdash; <span class="dc-title">Selects the default database for database queries</span></p>

 </div>

 <div class="refsect1 description" id="refsect1-function.maxdb-select-db-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>maxdb_select_db</strong></span>
    ( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$link</code></span>
   , <span class="methodparam"><span class="type">string</span> <code class="parameter">$dbname</code></span>
   ) : <span class="type">bool</span></div>

  <p class="para rdfs-comment">
   The <span class="function"><strong>maxdb_select_db()</strong></span> function selects the default
   database (specified by the <code class="parameter">dbname</code> parameter) to be
   used when performing queries against the database connection
   represented by the <code class="parameter">link</code> parameter.
  </p>
  <blockquote class="note"><p><strong class="note">Note</strong>: 
   <p class="para">
    This function should only be used to change the default database for the connection.
    You can select the default database with 4th parameter in <span class="function"><a href="maxdb_connect.html" class="function">maxdb_connect()</a></span>.
   </p>
  </p></blockquote>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.maxdb-select-db-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   成功时返回 <strong><code>TRUE</code></strong>， 或者在失败时返回 <strong><code>FALSE</code></strong>。
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-function.maxdb-select-db-examples">
  <h3 class="title">范例</h3>
  <div class="example" id="example-1400">
   <p><strong>Example #1 面向对象风格</strong></p>
   <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$maxdb&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">maxdb</span><span style="color: #007700">(</span><span style="color: #DD0000">"localhost"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"MONA"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"RED"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"DEMODB"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/*&nbsp;check&nbsp;connection&nbsp;*/<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">maxdb_connect_errno</span><span style="color: #007700">())&nbsp;{<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"Connect&nbsp;failed:&nbsp;%s\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">maxdb_connect_error</span><span style="color: #007700">());<br />&nbsp;&nbsp;&nbsp;exit();<br />}<br /><br /></span><span style="color: #FF8000">/*&nbsp;return&nbsp;name&nbsp;of&nbsp;current&nbsp;default&nbsp;database&nbsp;*/<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$result&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$maxdb</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT&nbsp;SERVERDB&nbsp;FROM&nbsp;USERS&nbsp;WHERE&nbsp;USERNAME='MONA'"</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$row&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$result</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">fetch_row</span><span style="color: #007700">();<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"Default&nbsp;database&nbsp;is&nbsp;%s.\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">]);<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$result</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">close</span><span style="color: #007700">();<br />}<br /><br /></span><span style="color: #FF8000">/*&nbsp;change&nbsp;db&nbsp;to&nbsp;non&nbsp;existing&nbsp;db&nbsp;*/<br /></span><span style="color: #0000BB">$maxdb</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">select_db</span><span style="color: #007700">(</span><span style="color: #DD0000">"XXXXXXXX"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/*&nbsp;return&nbsp;name&nbsp;of&nbsp;current&nbsp;default&nbsp;database&nbsp;*/<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$result&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$maxdb</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT&nbsp;SERVERDB&nbsp;FROM&nbsp;USERS&nbsp;WHERE&nbsp;USERNAME='MONA'"</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$row&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$result</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">fetch_row</span><span style="color: #007700">();<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"Default&nbsp;database&nbsp;is&nbsp;%s.\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">]);<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$result</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">close</span><span style="color: #007700">();<br />}<br /><br /></span><span style="color: #0000BB">$maxdb</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">close</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
   </div>

  </div>
  <div class="example" id="example-1401">
   <p><strong>Example #2 过程化风格</strong></p>
   <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$link&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">maxdb_connect</span><span style="color: #007700">(</span><span style="color: #DD0000">"localhost"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"MONA"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"RED"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"DEMODB"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/*&nbsp;check&nbsp;connection&nbsp;*/<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">maxdb_connect_errno</span><span style="color: #007700">())&nbsp;{<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"Connect&nbsp;failed:&nbsp;%s\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">maxdb_connect_error</span><span style="color: #007700">());<br />&nbsp;&nbsp;&nbsp;exit();<br />}<br /><br /></span><span style="color: #FF8000">/*&nbsp;return&nbsp;name&nbsp;of&nbsp;current&nbsp;default&nbsp;database&nbsp;*/<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$result&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">maxdb_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$link</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"SELECT&nbsp;SERVERDB&nbsp;FROM&nbsp;USERS&nbsp;WHERE&nbsp;USERNAME='MONA'"</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$row&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">maxdb_fetch_row</span><span style="color: #007700">(</span><span style="color: #0000BB">$result</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"Default&nbsp;database&nbsp;is&nbsp;%s.\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">]);<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">maxdb_free_result</span><span style="color: #007700">(</span><span style="color: #0000BB">$result</span><span style="color: #007700">);<br />}<br /><br /></span><span style="color: #FF8000">/*&nbsp;change&nbsp;db&nbsp;to&nbsp;non&nbsp;existing&nbsp;db&nbsp;*/<br /></span><span style="color: #0000BB">maxdb_select_db</span><span style="color: #007700">(</span><span style="color: #0000BB">$link</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"XXXXXXXX"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/*&nbsp;return&nbsp;name&nbsp;of&nbsp;current&nbsp;default&nbsp;database&nbsp;*/<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$result&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">maxdb_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$link</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"SELECT&nbsp;SERVERDB&nbsp;FROM&nbsp;USERS&nbsp;WHERE&nbsp;USERNAME='MONA'"</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$row&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">maxdb_fetch_row</span><span style="color: #007700">(</span><span style="color: #0000BB">$result</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"Default&nbsp;database&nbsp;is&nbsp;%s.\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">]);<br />&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">maxdb_free_result</span><span style="color: #007700">(</span><span style="color: #0000BB">$result</span><span style="color: #007700">);<br />}<br /><br /></span><span style="color: #0000BB">maxdb_close</span><span style="color: #007700">(</span><span style="color: #0000BB">$link</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
   </div>

  </div>
  <p class="para">以上例程的输出类似于：</p>
  <div class="example-contents screen">
<div class="cdata"><pre>
Default database is &lt;...&gt;.

Warning: maxdb_select_db(): -10709 Connection failed (RTE:database not running) &lt;...&gt;

Warning: maxdb_query(): -10821 Session not connected [] &lt;...&gt;

Warning: maxdb_close(): -10821 Session not connected [] &lt;...&gt;
</pre></div>
  </div>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.maxdb-select-db-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="maxdb_connect.html" class="function" rel="rdfs-seeAlso">maxdb_connect()</a> - Open a new connection to the MaxDB server</span></li>
    <li class="member"><span class="function"><a href="maxdb_real_connect.html" class="function" rel="rdfs-seeAlso">maxdb_real_connect()</a> - Opens a connection to a MaxDB server</span></li>
   </ul>
  </p>
 </div>


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